1. Field of the Invention
The present invention relates to electrical monitoring systems. More particularly, the invention relates to a monitoring system for monitoring a heart""s electrical activity and that triggers upon detecting a rising edge of a R-wave.
2. Discussion of the Related Art
The human heart is a very complicated organ that relies on both mechanical and electrical operation in order to properly perform. As with any complicated mechanism, problems can and do arise, and the heart is no exception. For example, over time the electrical pathways in the heart (which sequentially cause the muscles of the atria and ventricles to contract) may fail, thereby causing the heart to lose its rhythm, which is known as arrhythmia. In such a situation, the heart must be monitored and an external stimulation applied in order to return the heart to normal sinus rhythm. A patient""s heart rate must be monitored in many other situations, such as during most surgical procedures, as the patient""s heart rate is a good indication of the patient""s condition during such a procedure. For that reason, many electronic instruments used in medical procedures employ analysis of a patient""s heart rate. The electrocardiogram (xe2x80x9cECGxe2x80x9d) is one conventional method of determining not only the patient""s heart rate, but also for determining potential abnormalities in the patient""s heart muscle. As is well known to those of ordinary skill in the art, an ECG is a tracing of the changes of electrical potential that occur within the heart during a heartbeat. In the ECG, the first upward deflection due to contraction of the atria is referred to as a xe2x80x9cP-wavexe2x80x9d, while xe2x80x9cQ-wavesxe2x80x9d, xe2x80x9cR-wavesxe2x80x9d, xe2x80x9cS-wavesxe2x80x9d, and xe2x80x9cT-wavesxe2x80x9d are deflections due to the action of the ventricles.
Recently, automatic detection of the R-waves of the ECG has become important. Detecting R-waves allows for a precise measurement of the patient""s heart rate. Automatic detection relieves a surgeon or other trained professional from performing that function. Many of the methods proposed for detecting R-waves are not sufficiently accurate, due to the presence of noise such as power line interference, baseline drift and ECG amplitude modulation with respiration, electrosurgical noise, and the like. In addition, false readings can occur from pacing spikes and T-waves, which are unaccounted for by those proposed methods.
Furthermore, a conventional ECG uses surface-mounted electrodes to monitor the heart""s electrical activity, which has shortcomings for detecting rising R-waves. First of all, electrode contact noise often occurs in surface-mounted electrodes, which consists of transient interference caused by the temporary loss of contact between the electrode and the patient""s skin. In addition, electrode motion relative to a patient""s skin can cause changes in the impedance and consequently changes in the voltage measured. Thus, R-wave detection with surface-mounted electrodes suffers from numerous shortcomings.
Accordingly, it will be apparent that there continues to be a need for an Rwave detection device and method that is designed to account for noise and to avoid false readings from pacing spikes, T-waves, and the like. The present invention addresses these needs and others.
Briefly, and in general terms, the present invention in one illustrative embodiment is directed to an apparatus for detecting R-waves from a patient""s heart. The system is operative to sense the heart""s electrical activity, detect the rising edge of an Rwave, and generate a synchronous pulse signal in response thereto. The system is further designed in such a manner that it can continue to function properly during many types of arrhythmias, and does not trigger during T-waves or pacing spikes.
Thus, the present invention in one illustrative embodiment is directed to an apparatus for monitoring electrical activity of a heart and generating corresponding pulse signals upon the monitoring of predetermined conditions, comprising: an electrode that senses electrical activity of the heart; and a signal processor in communication with the electrode to receive electrical activity data from the electrode and determine the magnitude of the electrical activity, the signal processor being programmed to determine whether the magnitude of the electrical activity exceeds an adaptively determined threshold and, if so, to generate a corresponding pulse signal.
The present invention in another illustrative embodiment is directed to a method for determining electrical activity of a heart, including the steps of: detecting a magnitude of electrical activity of at least the ventricles of the heart; setting a threshold value; comparing the magnitude of the detected electrical activity of the ventricles with the threshold value; determining when the magnitude of the detected electrical activity exceeds the threshold value; and generating a corresponding pulse signal.